Waste salt or bittern is the residual liquid from the salt formation which cannot be precipitated again but can be obtained from the washing water remaining in the purification process. Bittern has high economic value of mineral salts such as MgCl2, MgSO4, KCl, and Br2. The element Mg in bittern can be used as a mineral forming struvite because magnesium is one of the components needed in the formation of struvite. Crystallization of the formation of struvite minerals occurs in equimolecular concentrations of Mg 2+, NH4 + and PO43 - in an alkaline state. The column reactor is equipped with a bulkhead which functions as a stirrer inside the reactor and is assisted by incoming air. Struvite solution (MAP) reacted can be formed from phosphoric acid, ammonium hydroxide, and bittern or salt waste as a source of magnesium with a molar ratio of 2: 1: 1. The pH variations run in the range of 7 to 11 and the reactor inlet air velocity between 0.25-1.25 L/min in a closed column reactor that is operated continuously. The resulting dry sludge was analyzed by XRD method for mineral characterization, SEM to determine the morphology of the crystals and XRF to determine the composition of struvite mineral.

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Struvite, also known as magnesium ammonium phosphate hexahydrate, is a white crystal with a chemical formula magnesium ammonium phosphate hexahydrate (MgNH4PO4.6H2O). Because of its phosphate content, struvite can be utilized as a fertilizer. Tempeh industrial effluent contains a high concentration of PO4, making it a possible struvite fertilizer producing material. The formation of struvite fertilizer is carried out by the aeration process. This process is able to increase the pH and homogeneity of the solution. The solution of Magnesium Ammonium Phosphate (MAP) is prepared by reacting tempeh industrial wasterwater, Magnesium Chloride (MgCl2), and Ammonium Hydroxide (NH4OH). The MAP ratios used are 1:1:1 and 3:1:1. The temperature was set at 30 °C and pH 9, the airflow rate was carried out at a rate of 0.25 - 1.25 liters per minute. Struvite crystals were analyzed using X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM). The best struvite fertilizer content is magnesium by 40.3% and phosphorus by 43.9% at an air flow rate of 1.25 liters per minute and a ratio of 3:1:1. Further development can be done by applying struvite fertilizers to plants.  Keywords: aeration, crystallization, tempeh industrial wastewater, struvite   ABSTRAK Struvite adalah kristal putih yang secara kimiawi dikenal sebagai magnesium amonium fosfat heksahidrat (MgNH4PO4.6H2O). Struvite dapat dimanfaatkan menjadi pupuk karena kandungan fosfat (PO4) di dalamnya. Limbah cair industri tempe memiliki kandungan PO4 yang cukup tinggi, menjadikan limbah cair industri tempe adalah bahan pembentuk pupuk struvite yang potensial. Pembentukan pupuk struvite dilakukan dengan proses aerasi. Proses ini mampu meningkatkan pH dan homogenitas dari larutan. Larutan MAP (Magnesium Amonium Fosfat) dibuat dengan cara mereaksikan limbah cair industri tempe, Magnesium Klorida (MgCl2), dan Amonium Hidroksida (NH4OH). Rasio MAP yang digunakan adalah 1:1:1 dan 3:1:1. Temperatur ditetapkan sebesar 30°C dan pH 9, laju alir udara dilakukan dengan laju 0,25 - 1,25 liter per menit. Kristal struvite dianalisis menggunakan Floresensi sinar-X (XRF) dan Mikroskop Pemindai Elektron (SEM). Kandungan pupuk struvite terbaik adalah magnesium sebesar 40,3% dan fosfor sebesar 43,9% pada konsentrasi 3:1:1 dan laju alir udara 1,25 liter per menit. Pengembangan lebih lanjut dapat dilakukan dengan mengaplikasikan pupuk struvite ke tanaman. Kata Kunci: aerasi, kristalisasi, limbah cair industri tempe, struvite

Bamboo shoots are buds in the root system of bamboo that grow and develop into young bamboo culm. The root system of bamboo, which has many internodes and buds produces many shoots but not all of them can grow and develop into bamboo shoots. Bamboo shoots can be used as a horticultural food commodity because they are usually harvested and consumed as a vegetable for several dishes. The purpose of this study is to analyze the financial feasibility of bambu ampel kuning (Bambusa vulgaris var striata) cultivation as a producer of bamboo shoots based on indicator criteria NPV, Net B/C, IRR, and payback period. Data are collected using field observations, interviews, and discussions with bamboo garden owners covering cultivation techniques, production facilities, and labor. The results show that the NPV value of Rp. 137,097,914.5 is greater than zero, the Net B/C of 2.309 is greater than one, the IRR value of 42% is greater than the interest rate used by 12%, and the payback period in the 5th year of the age of the bamboo shoot-producing business of 15 years. Based on the criteria for financial feasibility indicators, the cultivation of bambu ampel kuning (Bambusa vulgaris var striata) as a producer of bamboo shoots is feasible. We recommended cultivating bamboo shoots in marginal areas.

Struvite is a white crystal, chemically known as magnesium ammonium phosphate hexahydrate (MgNH4PO4.6H2O). Tofu factory liquid waste is waste that can be reused because of its content. Tofu factory liquid waste can potentially pollute the environment. This research aimsto analyze the manufacture of struvite by utilizing the phosphate content contained in the liquid waste of tofu factories using vertical canted column reactors which can reduce environmental pollution due to liquid waste of tofu factories. This study uses a vertical canted column reactors by mixing anequimolar 1: 1: 1 MgCl2: NH4OH: H3PO4 solution. Struvite crystallization process operates at a temperature variation of 30°C,35°C,40°C,45.50°Cand a pH of 8, 9,10,11,12 by maintaining the air rate of 0.5 liters minute-1 and a MAP (Magnesium Ammonium Phosphate)flow of 56 ml minutes-1 as a whole. The crystallization process runs until a steady state conditionis reached. Then, the struvite crystals obtained were filtered and dried at room temperature for 24 hours. After that struvite crystals were analyzed using XRF, XRD, and SEM. The results of the study obtained the best phosphate conversion of 24.935% at 30°C  and pH 8.